The field of the invention is systems and methods for medical imaging. More particularly, the invention relates to systems and methods for tracking the location of an interventional medical device, such as a catheter, using a medical imaging system, such as an x-ray imaging system.
The development of new percutaneous devices and treatment techniques has resulted in a significant increase in the use of x-ray guidance to perform minimally invasive therapies. Currently, x-ray fluoroscopy is the standard imaging modality used for guidance in interventional cardiology procedures. The two-dimensional x-ray projection images produced during fluoroscopy provide excellent visualization of interventional medical devices, but inherently lack depth information. In some procedures, such as electrophysiology procedures, it is important to return to the same anatomical location during the procedure. This task cannot be achieved solely by viewing the catheter in a two-dimensional x-ray image because precise manipulation requires three-dimensional localization.
Localization of interventional medical devices in three-dimensional space can be made possible by using bi-plane imaging system, in which a second x-ray view is acquired from a different perspective using a relative geometrical relationship between the first and second view. In anatomical sites subject to rapid motion, simultaneous acquisition from two perspectives is preferable but can only be achieved using a bi-plane catheterization system. These bi-plane catheterization systems are not common and result in increased x-ray radiation being delivered to the patient. Moreover, even for bi-plane systems, there is currently no x-ray based three-dimensional localization technology commercially available; rather, the operator usually relies on a visual estimate supported by a previously obtained roadmap image.
Three dimensional localization technologies using specially designed non-x-ray based catheter tracking systems have been developed and are commonly used clinically. One such system, called CARTO (Biosense Webster, Inc.; Diamond Bar, Calif.), relies upon a small magnetic field sensor located at the distal tip of the catheter. This magnetic field sensor is used to measure an induced magnetic field from external emitters located beneath a patient. Another system, called EnSite™ (St. Jude Medical, Inc.; St. Paul, Minn.), uses an impedance-based localization technique that employs either six external patches placed on a patient, or a multi-polar catheter positioned inside the heart, to track the interventional device. These systems provide accurate localization, but result in significant capital and per-use cost.
One method for three-dimensional localization of an interventional medical device from a two-dimensional x-ray projection image is disclosed in U.S. Pat. No. 6,574,493. In this method, a marker having a specific geometric arrangement is affixed to the interventional device to be tracked. When imaged in two-dimensions, the affixed marker provides an indication of its position and orientation on account of its known, and particular geometric arrangement. Because this method requires use of a specialized marker that is affixed to an interventional medical device, it is of limited clinical use. Namely, the method requires modification of existing interventional devices, and such modifications may negatively affect the performance and safety characteristics of the medical device being used.
Therefore, there exists a need to develop an inexpensive and robust method for tracking the position of an interventional medical device in three-dimensional space using the information available from a single, two-dimensional image acquired with a standard x-ray fluoroscopy system. Fluoroscopy suites are used as a standard imaging modality in virtually all hospitals and, therefore, additional cost to use such a three-dimensional localization technique would be quite low.